(a) Field of the Invention
This invention generally relates to a system and method for delivering bulk materials to an area where they will be processed More particularly, but without limitation to, a pneumatically activated delivery system for delivering particulate materials to a hopper or the like, and to a hopper and melt pot system that uses a peel-away melt pot cover together with a feed hopper that is positionable directly over the opening exposed by the peel-away melting pot cover.
(b) Discussion of Known Art
The need to deliver raw materials in bulk to a desired location for processing has produced many devices which address problems with contamination, reliability, maintainability, simplicity, and versatility. These problems are of particular importance in the adhesives industry, where granulated "chips" or particulates of solid glue material are delivered by a conveying system to a melting pot. In these systems, the chips are typically stored in a bulk storage container such as a tote bin or a "super sack" prior to delivery to the point of use.
The delivery of the unmelted glue pieces from the bulk storage container to the melting pot has typically been accomplished by the use of pneumatic conveying systems of one type or another. These systems have a number of disadvantages. Some of the most salient disadvantages include the following:
1) There is a limit to the size of the "chips" that can be transported. The upper limit is generally regarded as being pellets of about 3/8" in diameter. Bulk hot melt glues come in a variety of sizes and shapes, including sticks of up to approximately 1".times.3".times.1/4". Thus, known systems lack the versatility to carry many of the available bulk products. It is important to note that glue sticks, as well as pellets or other bulk forms of solid glue will be referred to herein as "particles."
2) Existing systems give significant opportunity for contamination or oxidation of the material being delivered. The use of air (or vacuum) to transport the product means that the product must be either dropped out in a cyclone type separator, or as is done in most cases, the air is exhausted into the glue melting pot where the combination of turbulence and oxygen in the air causes accelerated oxidation and charring of the glue. This, in turn, can subsequently plug application devices and cause down time on the production line.
3) Air transport systems, if not filtered adequately, can introduce contaminants into the glue.
4) Many bulk meltable glues are shipped with a "dust" coating which improves the handling characteristics of the bulk material by preventing the chips from adhering to one another. Thus, the transporting air or gas stream also picks up this dust coating on the hot melt glue. This dust must then be filtered out when the air is exhausted, creating a maintenance problem as well as possibly causing a troublesome build up of dust on equipment and processes.
5) Moving parts used in known systems can be easily fouled by vapors found in the working environment. The methods currently in use for actually placing the charge of unmelted glue particles or pieces into the melt pot involve placing equipment directly above the melt pot. Melted glue and the melt pot at operating temperature gives off a significant amount of vapors. These vapors condense on the equipment and result in a very sticky film that causes problems in operation after a short period of time.
6) The advent of reactive types of hot melt adhesives has introduced an increased sensitivity to the presence of oxidizing agents. For reasons outlined above, air or vacuum transport systems exacerbate this problem and current systems offer no means of preventing air from contacting the melted glue.
There remains a need for a bulk materials transport system which can transport a wide variety of hot melt glue sticks to a desired location for processing.
Furthermore, there remains a need for bulk solid glue particulate transport system which can prevent contamination or oxidation of the material being delivered.
Still further, there remains a need for a bulk materials transport system that does not require the use of air or other gases for transport, and thus prevents the accumulation and spreading of airborne dust.
Still further there remains a need for a system which uses few moving parts or parts which are not easily fouled by vapors found in the working environment.
There remains a need for a system that can deliver predetermined amounts of meltable glue to a melting pot while allowing the use of the delivery system with a means of preventing air from contacting the melted glue within the melting pot.